For manufacturing, everyday living and research purpose, sometimes it is needed to capture a small live animal. In the prior art, a valve type automatic door traps are used to capture the fox, mink, squirrels and other small animals. This kind of valve type automatic door trap comprises a cuboid shaped metal wire braided cage, having a front opening, the front opening of the cage is provided with a door panel, the upper edge of the door panel is connected with the cage by a hinge structure, a spring device is arranged between the lower edge of the door panel and the cage, the spring device make the lower edge of the door panel to lean towards the bottom surface of the cage, in order to close the cage. The bottom surface inside the cage is provided with a pedal, and the front side of the pedal and the cage bottom surface are connected through another hinge structure, a trigger mechanism is arranged between the pedal and the door panel. The lower edge of the door panel is raised manually to open the front side of the cage, lock the door panel at a ready position by a triggering mechanism, the back side of the pedal and trigger mechanism is linked and will be up lifted up in response to a trigger. Inside the cage, at the back end, bait is provided. When a little animal target gets into the cage, looking for the small animal bait, the forelimbs of the animal steps on the pedal and when the pedal receives pressure trigger mechanism linked with the pedal is activated, the door panel is unlocked and the front opening of the cage is closed as the door panel is lean toward the cage by the spring device, therefore the small animal is shut in the cage. A backstop mechanism is also arranged between the door panel and the cage, to prevent the forces from inside of the cage to make the door panel open. In the prior arts, the trigger mechanism between the pedal and the door panel often fails due to rust or the tight arrangement of trigger mechanism. Moreover, locking the door panel in a ready position manually adds a level of complexity in its everyday use.